What this test is for
Measure the voltage lost across a cable, terminal, ground, fuse link, or connection while the circuit is carrying the relevant load.
Use the procedure to narrow a cause group. The result must be interpreted against the exact vehicle, equipment, and conditions.
- 01PurposeMeasure the voltage lost across a cable, terminal, ground, fuse link, or connection while the circuit is carrying the re
- 02PrepareDigital multimeter / Appropriate circuit load
- 03MeasureDefine the current path / Apply the real load
- 04InterpretA test across the wrong points can produce a believable but irrelevant number.
- 05ContinueBattery voltage and condition test / Starter-circuit test
Follow the sequence, stop when evidence changes the path, and verify the exact vehicle information before acting.
Preserve the operating conditions, equipment setup, and result before moving to the next branch.
Tools and preparation
- Digital multimeter
- Appropriate circuit load
- Wiring diagram or service information
Procedure and interpretation
Define the current path
Identify source, load, power-side segments, and ground-side segments from the correct wiring information.
The test points represent one complete path under load.
A test across the wrong points can produce a believable but irrelevant number.
Apply the real load
Operate the circuit or use an approved load that matches the question being tested.
The fault condition is present while measuring.
A circuit can pass a continuity check and still fail when current flows.
Measure each segment
Measure across connections and cable sections, then compare the pattern with the vehicle or equipment limits.
The loss is not concentrated at an unexpected segment.
The highest supported loss identifies where to continue inspection, not automatically which part to replace.
Record this test result
Save a bounded result and note to the selected vehicle. This is a personal record, not a verified diagnosis.
Choose a vehicle in My Garage or the vehicle selector first. IAR will not attach a test result to an unknown vehicle.
What to test next
Safety boundary
Use the correct circuit and load
Do not pierce insulation or bridge high-current circuits casually. Use approved back-probing and protect against shorting adjacent terminals.